This invention relates generally to an apparatus for breaking apart agglomerated particulate matter and particularly for breaking up agglomerated sponge iron in a moving-bed vertical-shaft reduction reactor to maintain the mass flow of such particulate matter through the reactor and prevent a plugging of the typical convergently-restricted outlet. The present invention can also be more broadly employed to maintain the flow of other types of particulate or granular matter and to prevent the plugging of the outlet in similar applications.
In general, the production of sponge iron in a vertical moving-bed reactor involves two principal steps, namely, reduction of the ore with a suitable hot reducing gas in a reduction zone of the reactor and then subsequent cooling of the resulting sponge iron with gaseous coolant in a cooling zone of the reactor. Preferably, the reducing gas is largely composed of carbon monoxide and hydrogen at temperatures of the order of 750.degree. C. to 1100.degree. C., and more preferably 900.degree. C. to 1000.degree. C. and at pressures above atmospheric pressure. The hot reducing gas is usually introduced at the bottom of the reduction zone and passed upwardly through the reactor countercurrent to the particulate flow, to reduce the ore to metal. Cooling of the reduced sponge iron may be effected by a separate cooling loop (as in U.S. Pat. No. 3,765,872 issued Oct. 6, 1973, the disclosure of which is incorporated herein by reference) or by other known alternatives.
The solid ore particles or pellets are charged under pressure to the top of the moving-bed reactor. After reduction in the upper zone and cooling in the lower zone to a relatively low temperature, the sponge iron is discharged from a preferably conically convergent discharge outlet at the bottom of the reactor.
One problem in any continuous moving-bed reduction reactor system is the tendency of the sponge iron to cluster or agglomerate under certain operating conditions or through equipment failure as the sponge iron moves through the reactor. This tendency differs for different grades and sources of iron ore. Such agglomeration is affected by such factors as gangue composition of the iron ore. lumps or pellets, geometry of the latter or of the reactor, reducing gas composition, flow characteristics and solids residence time, processing temperatures and pressures and other not-fully determined variables. High operating temperatures can increase production and reduce capital cost, but also increase risk of agglomeration. Thus there is an incentive for the plant operators to run the process at as high temperatures as possible (in spite of agglomeration risks). When the sponge iron agglomerates in a moving-bed reactor system, the mass flow of the solids through the reactor is distorted, giving an uneven product. The movement of the sponge iron bed may even stop, thereby plugging the reactor at its outlet end and result in a costly shut down with concommitant production loss. If the plugging of the reactor is sufficiently great, serious damage to the reactor itself can also result. Also, an agglomeration, which is proportionally small in the large diameter portion of the reactor (e.g., in the reduction zone), can be significantly large at the constricted discharge outlet; so as to block flow unless broken up.
A need exists for an apparatus to break up internal clusters of agglomerated sponge iron to maintain the proper mass flow of the solids through the reactor without necessitating the shut down of the reactor to remove clusters and without impeding the flow of the ore mass which has been reduced in the reactor.
The problem of agglomeration has long been recognized in the prior art, particularly in the direct reduction of iron ore. The prior solutions to this problem have not been very practical in commercial operation; often creating additional problems. For example, most solutions involve reciprocating or rotating rakes which are permanently positioned within the reactor, causing obstruction to uniform flow and often directly subject to continuous abrasion and elevated temperatures (even when not needed). See for example U.S. Pat. Nos. 2,862,808 and 4,118,017.